New file msvcrt/excpt.h. Move some stuff out of winnt.h into it.

diff --git a/loader/resource.c b/loader/resource.c
index 6aee478..4967843 100644
--- a/loader/resource.c
+++ b/loader/resource.c
@@ -23,6 +23,7 @@
 #include "debugtools.h"
 #include "winerror.h"
 #include "winnls.h"
+#include "msvcrt/excpt.h"
 
 DEFAULT_DEBUG_CHANNEL(resource);